Daily Archives for April 15, 2018

It’s likely you’ve never heard of a hihi, let alone seen one in the wild. Also known as stitchbirds, these colourful little critters are a true taonga, or treasure. They’re only found in New Zealand, and currently restricted to just seven sanctuary sites.

Without the caché of kiwi or kākāpō, hihi have gone largely ignored by conservation fans and also, crucially, by funders. Researchers have been interested in these sunny little birds for decades because of their crazy mating system and high-octane lifestyle.

Researchers are studying sperm quality to figure out what contributes to the low breeding success of the hihi, or stitchbird.

A taonga in trouble

The story of hihi is a sadly familiar one for New Zealand. They were widespread across the country’s North Island, but then humans arrived. Forest clearance and introduced mammalian predators were bad news for most of New Zealand’s native wildlife, including hihi. By 1880, hihi had been reduced to just one population on Hauturu (Little Barrier Island).

Over the past 25 years or so, conservation managers and researchers have established six new hihi populations in predator free sanctuary sites around the North Island, and numbers are on the rise, but hihi are not out of the woods yet.

At each site except for Hauturu, hihi rely on supplementary sugar-water feeding. They use the energy from the sugar water to hunt insects – their real food. On Hauturu, they get their sugar from plant nectar, but no other site in New Zealand seems to have the diverse, old growth forest that hihi need.

Catching hihi on Tiritiri Matangi, one of the island sanctuaries where they survive, to get a sperm sample.Mhairi McCready, CC BY

Small populations and dodgy sperm

The hihi’s drastic decrease in numbers after human arrival is known as a population bottleneck. When a species experiences a bottleneck, we typically see a reduction in genetic variation and an increase in mating between relatives (inbreeding).

Studying bird sperm in the wild

I’m looking for links between inbreeding and sperm quality in native New Zealand birds, including the hihi. To measure bird sperm quality, we look at three things: sperm swimming speed, sperm length and the proportion of sperm with abnormalities (two heads/no tail etc.).

Getting this data from wild birds is challenging for a number of reasons.

First, you need to get the sperm. This is actually the easiest part, especially with hihi. Their mating system is so competitive that males are usually jam-packed with sperm during the mating season.

In most bird species (including hihi), males don’t have a penis. They have an opening called a cloaca, just like the female. During mating season, the area around the male’s cloaca swells as it fills up with semen. By gently massaging this swelling, I can cause a small amount of semen to pool on the surface of the cloaca and, voila! I have my sperm sample.

The next challenge is measuring sperm swimming speed. Everything else can be done back at the lab, but speed has to be measured there and then and sperm have to be kept at a constant temperature, or they die. We need to run a microscope, camera and laptop to film the sperm and measure the speed. And I’m usually on a remote island or in the middle of the bush.

To overcome these issues, I’ve designed a mobile sperm lab that runs off a small generator so I can take it pretty much anywhere. It houses my sperm speed measuring set up, plus some heat pads to keep anything that touches the sperm at a constant temperature.

The pièce de résistance is my specially designed in-bra sperm sample tube holder, which keeps samples warm against my skin before they get to the microscope.

The great hihi sperm race

I collected sperm and DNA samples from 128 males and am currently analysing the data to investigate the connection between sperm quality and inbreeding in this species.

At the same time, we’re attempting to address the major lack of funding for hihi conservation by encouraging people to bet on which of my 128 males will have the fastest sperm.

This innovative fundraiser has grabbed a fair fewheadlines in New Zealand and overseas, and we’ve seen bets coming in from all over the world. The race runs until April 22, 2018. To get involved, visit www.hihispermrace.nz and place your bets!

The Australian Bureau of Meteorology’s latest climate outlook, issued today, suggests the above-average warmth of April is likely to extend into May, and for parts of the south, potentially into winter.

The outlooks for May temperatures show that both days and nights are likely to be warmer than average for much of Australia. Only northeast Queensland is likely to miss out on warmer temperatures, with no strong push there towards warmer or cooler conditions.

The unseasonable warmth, which has broken records in Adelaide and Sydney, appears to be driven by high ocean temperatures, and weaker westerly winds and much lower than average soil moisture across southern Australia.

Bureau of Meteorology

The rainfall outlook for May is mixed, but generally shows no strong shift towards a wetter or drier month for most of Australia.

By June the tendency for warmer than normal days may start to wane. This easing of the outlook for above average temperatures as we head into winter is reflected in the full May-July outlook, with only some parts of southern Australia likely to be warmer than average. Southern parts of Western Australia and South Australia have a moderate chance of warmer than average daytime temperatures, with stronger odds over southern Victoria.

The full May to July outlook shows a more balanced picture, with southern Australia more likely to experience higher than average temperatures.Bureau of Meteorology

Odds don’t favour a strong push towards a particularly wet or dry three months for much of Australia, apart from some areas in the far southeast.

What’s behind the warmth?

The El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are two of Australia’s major climate drivers. ENSO is currently in a neutral phase, meaning its neither El Niño nor La Niña. Our outlooks suggest it is likely to stay neutral leading into winter.

The IOD is also neutral, and most models suggest it will remain so over the coming months.

But given it is harder to forecast ENSO and the IOD in autumn compared to other times of the year, climatologists will be monitoring Indian and Pacific Ocean temperature patterns closely as we edge towards winter.

With near-average temperature patterns in the tropical oceans to our east and west, there is no strong shift in the outlook towards widespread wetter or drier conditions for Australia.

Rainfall during May is expected to remain essentially average.Bureau of Meteorology

However, for temperatures it’s a little different. Sure ENSO and the IOD are playing a minor role right now, but other factors are coming into play.

Ocean heat waves

Ocean temperatures in the Tasman Sea and around New Zealand are much warmer than average – in fact at record levels in the past few months – and are expected to remain warm over the coming months. These warm sea temperatures are associated with a large area of lower than usual air pressure to Australia’s east, which is likely to weaken the westerly winds that normally bring cooler air to southern Australia in autumn and winter.

Another factor in the current and forecast warmth is the very much below average soil moisture across southern Australia. With little moisture available to evaporate and cool the air, and the soils themselves not able to store as much heat, the air above the ground heats more rapidly in the daytime.

Bureau of Meteorology

In addition to our natural climate drivers, Australian climate patterns are being influenced by the long-term trend in global air and ocean temperatures. Winter maximum temperatures have increased by 1℃ over the past century, with three of the top five warmest winters in the past 108 years occurring since 2009. Oceans around Australia have warmed by slightly more, with four of our top five warmest years since 2010.

So while the normal big two drivers of our climate remain benign, it would actually be wrong to assume there will be a quick return to more average temperatures. The outlook released today suggests we may have to wait at least another month until service returns to normal for much of the country.